AWUS01 KWNH 231634
FFGMPD
ALZ000-MSZ000-LAZ000-232130-

Mesoscale Precipitation Discussion 0060
NWS Weather Prediction Center College Park MD
1234 PM EDT Tue Mar 23 2021

Areas affected...southern LA into southern MS/southwestern AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 231633Z - 232130Z

SUMMARY...Periods of training heavy rain with rates of 2-3 in/hr
are likely to impact portions of the central Gulf Coast into the
mid-afternoon. Additional peak rainfall totals of 3-5 inches are
expected through 21Z. Given high flash flood guidance values
across the region, flash flooding may be limited to locations of
ideal cell training and sensitive urban locations, including the
city New Orleans.

DISCUSSION...Regional radar imagery at 16Z showed a line of strong thunderstorms extending from south-central MS into south-central
LA. The area of convection formed along a pre-frontal convergence
axis located off of the upper TX coast, extending into southern
LA, but has since become outflow dominant toward the south and
east. Infrared satellite imagery evidenced a strongly diffluent
flow pattern aloft over the central Gulf Coast and precipitable
water values have measured 1.5 to 1.7 inches within the NE to SW
oriented rainfall axis. Bowing segments within the convective line
have allowed for short term training to occur, with rainfall rates
between 2-3 in/hr at times, such as northern St. Helena Parish
through 1530Z.

Deeper layer mean flow (850-300 mb) is aligned with the
orientation of the convective line, southwest to northeast,
supporting training where the line slows or stalls forward
progress. This has been occurring over southern portions of the
convective line (near the Gulf Coast) over the past 1-2 hours,
whereas northern portions have been progressing more quickly to
the east.

Over the next 3-5 hours, the line of convection should continue to
translate eastward, with the northern portion possibly weakening
where instability is reduced. The intensity of the line should be
maintained across southern portions (roughly along and south of
I-10) where MLCAPE is expected to remain 500-1000 J/kg well into
the afternoon. The greatest potential for additional training and
heavy rain will be across southern portions of LA where
uninhibited access to rich Gulf Moisture and slower eastward
movement of the convective line is expected. Additional totals
through 21Z of 3 to 5 inches are expected.

Otto

ATTN...WFO...JAN...LCH...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 31418937 31318831 31048781 30418792 29748893
29188991 29079110 29439220 29509271 29829292
30229265 30279176 30589100 31239046

$$
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AWUS01 KWNH 270842
FFGMPD
TNZ000-KYZ000-ALZ000-MSZ000-271500-

Mesoscale Precipitation Discussion 0072
NWS Weather Prediction Center College Park MD
441 AM EDT Sat Mar 27 2021

Areas affected...Tennessee

Concerning...Heavy rainfall...Flash flooding likely

Valid 270840Z - 271500Z

Summary...Thunderstorms expected to develop and track over the
region this morning will have the potential to produce hourly
totals up to 2". Through 15Z, 2-3"is possible with some potential
near4" and this is likely to cause some instances of flash
flooding, especially over portionsof middle Tennessee where soils
are more saturated from recent rainfall.

Discussion...In response to a broad area of large scale forcing
for ascent from the right entrance region of a jet streak over the
Ohio Valley and the eventual approach of shortwave energy from the
Plains, a northward advancing warm front through Mississippi and
Alabama this morning will help initiate/focus convection over
portions of Tennessee. The environment will rapidly evolve during
this time with a surge of MUCAPE of 2000-2500 J/kg and a rapid
increase in precipitable water to 1.3-1.4". Dewpoints, currently
in the 40s over TN, will increase well into the 60s this morning.
850 mb flow impinging on the boundary is expected to increase to
around 35 kts. Storms should initiate closer to 12Z and track east/northeasterlyand with the mean flow nearly aligned to the
storm motions, repeating rounds are likely.

The 00Z hi-res guidance shows reasonable agreement for a stripe of
2-3" through about 15Z, particularly across middle Tennessee. The
06Z HRRR shows an uptick in QPF, with localized 3-4" totals
through 15Z in and around the Nashville metro region, which is
concerning. Hourly totals between 1-1.5" are likely at times after
13Z and there is some signal for near 2" totals as seen in the
HRRR. The last several runs of the HRRR have been very consistent
with this signal.

Much of this area is running precipitation surpluses 150-300
percent of normal the last 14 days. The lowest flash flood
guidance is across middle Tennessee where 1-hr FFGs are 1.5". As
such, some instances of flash flooding will be likely after 12Z
and continuing through the remainder of the morning hours.

Taylor

ATTN...WFO...HUN...JKL...LMK...MEG...MRX...OHX...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 36708426 35988383 35098545 34828845 35578922
36288799 36638655

$$
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AWUS01 KWNH 270959
FFGMPD
TNZ000-MSZ000-ARZ000-271557-

Mesoscale Precipitation Discussion 0073
NWS Weather Prediction Center College Park MD
558 AM EDT Sat Mar 27 2021

Areas affected...vicinity of southwest TN

Concerning...Heavy rainfall...Flash flooding possible

Valid 270957Z - 271557Z

Summary...Showers and thunderstorms are beginning to show training
character in this area. Hourly rain totals to 2.5", along with
local amounts to 4", are possible over the next several hours.

Discussion...A weak surface wave appears to be forming in eastern
Arkansas at 09z, which is causing convection to backbuild to some
degree and begin to show training character as of late. Water
vapor imagery shows a weak shortwave approaching from the ArkLaTex
at this time within an environment of diffluence aloft between the
subtropical jet and the southern stream jet. Precipitable water
values are quickly rising towards 1.5" per recent GPS data across
northern MS. Inflow at 850 hPa is out of the southwest at 35
knots per area VAD wind profiles, with effective bulk shear to
match, which is quasi-parallel to the 850-300 hPa wind. This
inflow is importing 2000+ J/kg of MU CAPE into the area.

Forecasts from the 00z GFS show increasing 1000-500 hPa thickness
diffluence in this area, which could support the
formation/continued development of a convective complex, which
sooner or later should try to expand the convective footprint or
possibly forward propagate the activity to the east over the next
several hours into the area of MPD #072. With the thickness
pattern otherwise remaining status quo, the thunderstorm area may
not show much northerly movement this morning. Instability is
expected to envelop this convective complex with time, which may
increase rainfall efficiency. The only piece of mesoscale
guidance to indicate heavy rain in this area over the next several
hours is the 00z Canadian Regional model, which shows 2"+. The
ingredients available support hourly rain totals to 2.5" where
cells train -- problematic in urban areas or otherwise -- and
local amounts in the 4" are considered possible. As two week
precipitation in this area has been 150-200% of normal, soils are
more sensitive than usual, so flash flooding is considered
possible.

Roth

ATTN...WFO...LZK...MEG...OHX...

ATTN...RFC...LMRFC...NWC...

LAT...LON 35988862 35728798 35008873 34279085 34499177
35129101

$$
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AWUS01 KWNH 271945
FFGMPD
TNZ000-MSZ000-MOZ000-ARZ000-280000-

Mesoscale Precipitation Discussion 0075
NWS Weather Prediction Center College Park MD
344 PM EDT Sat Mar 27 2021

Areas affected...Southeast Arkansas

Concerning...Heavy rainfall...Flash flooding possible

Valid 271944Z - 280000Z

Summary...The threat of heavy to excessive rainfall will be
increasing over parts of southeast Arkansas and a small portion of
neighboring states this afternoon.

Discussion...Thunderstorms capable of producing heavy rainfall are
expected to develop over the southeastern part of Arkansas during
the afternoon in an increasingly moist and unstable atmosphere.
Precipitable water value have been slowly climbing to values at or
above 1.5 inches during the morning and early afternoon over far
eastern Arkansas. Low level flow, which was beginning with 850 mb
speeds around 30 kts at 1830Z based on area 88D VAD wind profiles
and 18Z soundings from LZK and SHV, will help to focus and
strengthen low level moisture flux convergence throughout the day
along a moisture gradient/stationary front separating dewpoints in
the upper 60s over southeast Arkansas from dewpoints in the 50s to
near 60 degrees farther north and west.

High resolution guidance has been consistent in advertising the
uptick in convection developing across the area between 20Z and
2230Z across the area and continuing to increase in coverage into
the evening. Current thinking is that rainfall rates may not
initially be high enough to produce more than limited coverage of
flash flooding, but the risk of flash flooding increases
throughout the afternoon and early evening as rainfall
rates/amounts increase and the ground (which is already wet from
previous events) becomes saturated over an increasing area.

Bann

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 36388964 35378969 34319060 33429169 33429320
34469350 35339209 35889108

$$
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AWUS01 KWNH 101231
FFGMPD
FLZ000-GAZ000-101600-

Mesoscale Precipitation Discussion 0097
NWS Weather Prediction Center College Park MD
830 AM EDT Sat Apr 10 2021

Areas affected...Western Florida Panhandle...

Concerning...Heavy rainfall...Flash flooding possible

Valid 101230Z - 101600Z

SUMMARY...Decaying MCS with quick bust of 1-2" totals reaching
areas affected by heavy rainfall yesterday. Rapid inundation is
possible.

DISCUSSION...GOES-E and Regional RADARs depict the leading edge of
squall line crossing the western tip of the FL panhandle
continuing to progress quite quickly. EIR denotes recent warming
of the deepest convection denoting the slow decay of the squall
line has begun in earnest, as instability pool ahead of the line
continues to restrict in size and limit itself strictly to the
Gulf waters were there remains slightly higher moisture and
thermal spread. Forward progression combined with 10-15kts of SSE
flow off the warm Gulf will continue to provide very strong
moisture flux convergence for the next 2-4 hours resulting in
sub-hourly rainfall totals around 1.5-2.5" with the bulk (1-2") in
15-30 minutes). This alone will cause rapid inundation on
non-permeable (ie, urban) grounds, however, recent heavy rainfall
over the last day with broad 3-7" totals (mainly maximized along
the coastal zones of Bay, Gulf and w Franklin counties are more
likely to see enhanced run-off and inundation rapidly given
saturated ground conditions and swollen streams. Still, with the
slow decay and weakening of moisture flux convergence into the
leading edge of the line.

Though the MCV/bookend vorticity center is expected to lift
north-northeast which may slow forward speed ever so slightly to
counter-act some of the reduction of rain rates further east into Liberty/Calhoun counties by late morning hours, as the upstream
squall line crossing Mobile Bay currently, catches the leading
bow.

Gallina

ATTN...WFO...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 30918661 30908518 30658408 30368398 30028405
29538477 29508530 29828559 30038592 30128705
30648717
$$
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AWUS01 KWNH 102043
FFGMPD
VAZ000-NCZ000-SCZ000-GAZ000-TNZ000-110130-

Mesoscale Precipitation Discussion 0098
NWS Weather Prediction Center College Park MD
443 PM EDT Sat Apr 10 2021

Areas affected...Northeast GA...Upstate SC...Western
NC...Southwest VA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 102045Z - 110130Z

SUMMARY...Increasing thunderstorm activity with capability of 1-2"
totals across complex terrain may result in isolated flash
flooding conditions through the late evening.

DISCUSSION...GOES-E WV denotes shortwave in the broad
southwesterly flow moving through north-central GA providing solid
low level backing wind field response across the Piedmont of the
Carolinas in the foothills of the Appalachians. Cloud cover has
limited ideal insolation, but some filtered sun has supported a
few degree spread in Temps over the mid-60s Tds across the
foothills. 19z RAP soundings and Layered PW analysis suggest
nearly saturated lower profile from Sfc to 5H. So with narrow
skinny MLCAPES of 250-500 J/kg and the strong DPVA from the
shortwave, convection is starting to break out along/just ahead of
the shortwave with more scattered cells dotted along the foothills
across NC into SW VA. Without stronger instability, updraft cores
will be very small narrow well in advance of the shortwave but may
help to add up to .5" totals before the more significant/dense
convective cluster developing in GA attm. PW analysis suggests a
narrow ribbon of PW up to 1.5" along/ahead of the wave, but with
30-40kts of deep southerly flow, oblique but strong moisture flux
convergence appears to support up to 1.5"/hr rain rates. The
orientation of the steering flow to the inflow may not be ideal
for flux, but will be solid for elongated or trailing flanking
lines that could support longer duration. Key factor to greater
rainfall efficiency will be the Sfc flow maintaining the stronger
upslope orthogonal to the cells aiding the rainfall
efficiency...which is currently present but only 5-10kts. Recent
HRRR solutions have shown best initiation and timing/evolution
compared to the WRF solutions providing some confidence in 1-2"
rainfall totals through 01z.

Flash flooding concerns are likely to be limited to isolated
pockets, especially in typically susceptible complex terrain or
upper reaches of watersheds, in particular across Upstate SC and
western NC where ground conditions have been below normal.
Further up the spine of mountains, those become normal to slightly
above normal saturation across SW VA per NASA SPoRT 0-40cm soil
moisture over 70% and AHPS anomalies of 100-150%. As such flash
flooding is considered possible through 00z, but more probable
further north with time as cells mature too.

Gallina

ATTN...WFO...FFC...GSP...MRX...RNK...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

LAT...LON 37078078 36578034 35428142 34728217 34348279
34238328 34628356 35658275 36728159
$$
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AWUS01 KWNH 131743
FFGMPD
MSZ000-LAZ000-132215-

Mesoscale Precipitation Discussion 0102
NWS Weather Prediction Center College Park MD
143 PM EDT Tue Apr 13 2021

Areas affected...South Louisiana into far Southern MIssissippi

Concerning...Heavy rainfall...Flash flooding possible

Valid 131638Z - 132215Z

Summary...Thunderstorms continuing over southern Louisiana will
continue to spread east. The risk of flash flooding remains
isolated with hourly rain totals to 2" and local additional
amounts to 4" through the rest of the afternoon.

Discussion...A weak impulse is moving over a surface trough along
the LA coast which is aiding lift in a rather moist environment.
Precipitable water values have increased to around 1.9" in
south-central LA (2.5 standard deviations above normal) which is
moving into a dryer airmass farther east with a sharp moisture
gradient along the MS/AL coasts per recent RAP analysis.
Convective activity is becoming more surface based and is focused
farther south than activity from this morning with SBCAPE
generally 1500 to 2000J/Kg along the southern LA coast. WSWly deep
layer flow around 25kt and light WNWly propagation vectors will
continue to allow eastward movement across southeast LA (including
NOLA) to far southern MS this afternoon.

Guidance has struggled to have activity as far east as it has
been, meaning the earlier elevated activity was feeding on
instability that had progressed more than anticipated. Now that
the activity is more rooted from the surface trough, the activity
should generally expand south as it moves east. Quite a line is
setting up along I-10 west of Lake Pontchartrain that should allow
at least some training cells over the susceptible NOLA metro area
this afternoon and cause at least some urban flash flooding.
Hourly rain totals of 1.5" to 2" with local additional afternoon
rainfall of up to 4" are expected from a combination of
backbuilding, cell training, and cell mergers. Southern LA has
been rather wet over the past week, enhancing the flash flood
threat roughly along and south of I-10 this afternoon.

Jackson

ATTN...WFO...LCH...LIX...

ATTN...RFC...LMRFC...NWC...

LAT...LON 30829023 30718942 30368909 29838936 29358990
29559158 29739288 29919348 30289318 30369263
30419201 30609118

$$
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AWUS01 KWNH 141315
FFGMPD
LAZ000-TXZ000-141913-

Mesoscale Precipitation Discussion 0104
NWS Weather Prediction Center College Park MD
914 AM EDT Wed Apr 14 2021

Areas affected...Southern Louisiana

Concerning...Heavy rainfall...Flash flooding likely

Valid 141313Z - 141913Z

Summary...Thunderstorms tracking across southern Louisiana this
morning will be capable of producing hourly totals up to 2". Some
3-5" totals through 2 PM CDT will be possible and this could lead
to flash flooding.

Discussion...Elevated thunderstorms over central Louisiana and
southwest Mississippi is reinforcing a surface/outflow boundary
over southern Louisiana while regional radar shows another complex
of thunderstorms organizing over southeastern Texas and far
southwest Louisiana. MRMS is estimating 2"+ hourly totals with
this complex already. This activity is along the surface
instability gradient and the nose of the better low level moisture
transport, per the recent RAP mesoanalysis. PWs are anomalously
high, in the 1.7 to 1.8 inch range. The expectation is that SBCAPE
should build slightly northward, upwards of 2000-3000 J/kg by late
morning, while the complex organizes into a possible MCS and rides
eastward along the outflow/instability gradient. While the
activity should be a bit more progressive, rain rates should be
more intense and hourly totals 2" will be possible (per 00Z HREF probabilities). As the complex moves toward south-central
Louisiana, soil saturation is much higher and FFG is considerably
lower after recent heavy rainfall. In many areas, the 1-hr FFG is
1" or less and the expected thunderstorms should be able to exceed
this threshold. As such, some instances of flash flooding are
likely. For the most sensitive/saturated areas, some of the flash
flooding could be more significant.

Taylor

ATTN...WFO...HGX...LCH...LIX...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 30999268 30639159 30429046 29988996 29618978
29318986 29149022 29169075 29359119 29499167
29599239 29779342 29459475 30379431 30759406
$$
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AWUS01 KWNH 180909
FFGMPD
FLZ000-181505-

Mesoscale Precipitation Discussion 0110
NWS Weather Prediction Center College Park MD
508 AM EDT Sun Apr 18 2021

Areas affected...portions of the central and northern FL Peninsula

Concerning...Heavy rainfall...Flash flooding possible

Valid 180905Z - 181505Z

Summary...Rainfall rates of 1-2 in/hr and additional rainfall
totals of 2-4 inches are expected to impact portions of the
north-central FL Peninsula over the next 3-6 hours. Given the
expected overlap of additional rainfall with heavy rain that fell
on Saturday, flash flooding will be possible.

Discussion...Loops of GOES 16 infrared satellite imagery through
09Z showed expanding convection over the eastern Gulf of Mexico
with several strong updrafts near 28N 87W, located just north of a quasi-stationary front. An axis of anomalous moisture (90-95th
percentile for mid-April) was located near and north of the
stationary front with precipitable water values ranging from about
1.6 to 1.8 inches (per 00Z RAOBs and GOES 16 derived data). Local
radar data and surface observations also placed an outflow
boundary from earlier storms which has slowed forward movement
into northern Pinellas and Hillsborough counties as of 09Z. The
most recent (08Z) SPC mesoanalysis estimated weak elevated
instability of less than 500 J/kg across the north-central FL
Peninsula with values over 1000 J/kg to the south of the
stationary front.

Over the next 3-6 hours, short term guidance is unanimous with the strengthening of southwesterly low level flow over the eastern
Gulf by about 10 kt into the west coast of FL, with flow riding
atop the boundary, which will help to support increasing
convection beyond 12Z into the FL Peninsula. There is some
uncertainty regarding whether convection will form north of the
outflow boundary, stationary front or both. Despite the cloud
cover, some increase in instability is expected after sunrise
which will help to support enhancement to rain rates. The west to
east oriented surface to 850 mb convergence axis is aligned with
850-300 mb mean-layer winds, which will allow for repeating cell
movement. Rainfall in parts of Levy, Marion, Putnam and Flagler
counties has totaled 3 to 6 inches over the past 24 hours.
Expected overlap of additional heavy rain with rates of 1-2 in/hr
may cause localized flash flooding in these locations, as well any
sensitive urban locations outside of where the 3-6 inches of rain
fell on Saturday. An additional 2-4 inches of rain will be
possible through 15Z.

Otto

ATTN...WFO...JAX...MLB...TAE...TBW...

ATTN...RFC...SERFC...NWC...

LAT...LON 29648117 29618092 29128072 28738049 28498045
28328112 28248210 28098280 27968309 28328316
28858324 29228335 29268337 29418288 29608199
$$
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AWUS01 KWNH 182113
FFGMPD
FLZ000-190230-

Mesoscale Precipitation Discussion 0111
NWS Weather Prediction Center College Park MD
512 PM EDT Sun Apr 18 2021

Areas affected...Northern Florida Peninsula...

Concerning...Heavy rainfall...Flash flooding possible

Valid 182115Z - 190230Z

SUMMARY...Training Cells Capable of 2"+/hr rates and saturated
grounds support possible rapid inundation/flash flooding concerns
through late evening hours.

DISCUSSION...GOES-E WV suite depicts a solid shortwave
south-southeast of the Mouth of the Mississippi River advancing
eastward with broad upper level divergence downstream across the
northeastern Gulf of Mexico. As such, a surface inflection is
enhancing along an SW-NE oriented boundary and enhancing southerly
flow across the West Coast the peninsula with 10-15kt flow
strengthening to 20-25kts from surface to 850mb as the shortwave
approaches. The frontal zone is draped across the Peninsula from
BKV to south of MCO, north of VRB anchored by outflow from earlier
convective outflow.

Within the warm sector, Tds are over 70F though 850-7H LPW
suggests western Atlantic source of drier air...so instability is
sizable with MLCAPEs over 2000 J/kg, suggesting some dry air
entrainment may result closer/south of the frontal boundary, but
still low level inflow would be very moist, so surface based cells
will have ample entrainment to produce some moisture flux
convergence to slowly saturate profiles for increased rainfall
efficiency well after maturity. LPW also denotes a more deeply
saturated environment across the Panhandle and far northern
Florida with deepest moisture of 1.75 to 2" along the frontal
zone/inverted surface trof axis along/ahead of shortwave
height-falls. Deep unidirectional flow north of the surface
boundary along the 850mb trof axis would have greater moisture
availability though instability would have sizable reduction
given the narrower profiles with at most MUCAPE of 1000-1250 J/kg.
As such, a narrow axis from Levy/Citrus county to Flagler/N
Volusia county would be the intersection of best instability and
moisture. Strong convective cores along this axis will have the
capability of producing quick burst (1.25"/15mins per HRRR) rates,
particularly as best forcing and maturity of convective
development occurs nearer to 23-00z along/near NW Florida coast.

Cells should be quick moving but have a training orientation
resulting in rainfall totals of 2-3" are possible but could even
reach 4" in very isolated locations through 03z. If the training
axis remains fairly stable, which current trends suggest given
amplitude of the wave approaching, the axis of heaviest rainfall
may track through areas saturated late last evening with 2-3" from
Marion to Flagler county,resulting in area of greatest risk for
rapid inundation/flash flooding.

Some dry air entrainment could result in cold pools that could sag
the axis south, where ground conditions are a bit better but AHPS
weekly anomalies are well over 300% of normal. NASA SPoRT Soil
Saturation through 0-40 cm are fully saturated across the
Panhandle into northern Florida (over 98%) while below 70% across
the I-4 corridor, though has greater urban settings and more
hydrophobic high-runoff capability. As such, have encompasses
these areas into the area of concern.

Gallina

ATTN...WFO...JAX...MLB...TAE...TBW...

ATTN...RFC...SERFC...NWC...

LAT...LON 30108184 30018122 29288088 28168041 28028106
28158203 28328281 28598287 28888288 29438334
29868352 30058258

$$
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AWUS01 KWNH 231913
FFGMPD
TXZ000-240110-

Mesoscale Precipitation Discussion 0112
NWS Weather Prediction Center College Park MD
312 PM EDT Fri Apr 23 2021

Areas affected...South-Central to Southeast TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 231910Z - 240110Z

SUMMARY...Heavy showers and thunderstorms will be expanding in
coverage and organization going through the afternoon hours. A
combination of some localized training of convection and enhanced
rainfall rates will drive an increasing threat for some flash
flooding.

DISCUSSION...The latest GOES-16 WV suite shows a southern stream
shortwave trough ejecting east out into the southern High Plains
which will be interacting with an increasingly moist and unstable
airmass pooling across south-central to southeast TX in vicinity
of a northward advancing warm front, and this is expected to
result in a widespread area of heavy showers and thunderstorms
over the next several hours.

Already the latest VAD wind profiler data shows a 30 to 40
southerly low-level jet nosing up across areas of south-central to
southeast TX, with a pool of PWs approaching 1.75 inches. In fact,
the latest CIRA-LPW data shows a well-defined and fairly
substantial pool of low-level tropical moisture lifting north out
of the western Gulf of Mexico, and in the 700/500 mb layer there
is a bit of an eastern tropical Pacific moisture connection in
association with the subtropical jet.

The airmass pooling along the aforementioned warm front continues
to destabilize with MLCAPE values approaching 1500 j/kg as a
result of continued solar insolation. As the upstream shortwave
trough approaches over the next couple of hours, there will be a
notable increase in large scale ascent from increasingly divergent
flow aloft. This will be coinciding with an axis of stronger
moisture convergence/forcing along the front and should result in
a significant increase in the coverage and organization of
convection.

Given the available moisture transport and rather high PW
environment, the rainfall efficiency should be quite high, with
some hourly rainfall amounts of 2 to 2.5 inches possible, and
especially with the more organized and deeper convective cores in
time.

The latest HRRR and experimental WoFS guidance support a
likelihood for the convection to gradually organize along and just
north of the front and take on some training characteristics with
a cell motion increasingly off to the east-northeast. The training
set-up will favor some very heavy rainfall totals. The latest HRRR
guidance supports as much as 3 to 5 inches of rain with isolated
heavier amounts going through 00Z. This will increase the threat
for at least some flash flooding as a result over the next several
hours.

Orrison

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON 31639422 31479378 31119365 30659384 30269462
29779652 29629774 29659827 30019846 30549791
31049690 31369597 31599504
$$
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AWUS01 KWNH 242148
FFGMPD
GAZ000-ALZ000-250345-

Mesoscale Precipitation Discussion 0118
NWS Weather Prediction Center College Park MD
547 PM EDT Sat Apr 24 2021

Areas affected...Southeast AL...Southern GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 242145Z - 250345Z

SUMMARY...Some pockets of flash flooding will be possible going
into the evening hours from areas of repeating and/or training
showers and thunderstorms, and especially over areas that saw
heavy rain earlier in the day.

DISCUSSION...The late-day GOES satellite imagery shows broken
clusters of heavy showers and thunderstorms impacting areas of
southeast AL and southern GA as a strong southwest low-level jet
(40 to 50 kts) continues to aim in off the northern Gulf of Mexico
and interacts with a well-defined outflow boundary and adjacent
cold pool. This cold pool continues to be convectively reinforced
and has been the catalyst for several areas of repeating and
locally training convection over the last several hours. The
low-level jet is enhancing the moisture/instability transport into
region, and the latest visible satellite imagery shows some
well-defined cloud street activity from southern MS east through
southern AL and into the western FL Panhandle which is suggestive
of a notably moist and unstable boundary layer.

In fact, MLCAPE values are on the order of 2000 to 2500 j/kg
across southern MS and southwest AL which is seen pooling out
ahead of an approaching cold front. This is the result of strong
diurnal heating and moisture-rich surface dewpoints that have
risen into the low 70s. Overall, there is a fairly large area of
PWs on the order of 1.5 to 1.75 inches in place, and this coupled
with the low-level jet is again fostering rather high rainfall
efficiency with enhanced rainfall rate potential.

The aforementioned cold front is associated with a mid-level
trough advancing into the TN Valley and this will gradually be
sweeping east across the Southeast going into the overnight hours.
However, at least in the short-term, there will continue to be a
favorable environment across areas of southeast Al and southern GA
for repeating showers and thunderstorms, and some training of more
organized convective line segments.

The latest HRRR guidance supports additional rainfall amounts of 3
to 5 inches locally going through 03Z. This will be locally
falling on top of some areas that have seen heavier rain earlier
in the day, and therefore there will be some elevated runoff
concerns. Some pockets of flash flooding will be possible as a
result going into the evening hours.

Orrison

ATTN...WFO...BMX...CHS...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 32438470 32378390 32078217 31828133 31318122
31068141 30928210 30928269 30928343 30998443
31098497 31168545 31258597 31538638 31918633
32298587 32428534

$$
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AWUS01 KWNH 271908
FFGMPD
KSZ000-NEZ000-COZ000-WYZ000-272335-

Mesoscale Precipitation Discussion 0119
NWS Weather Prediction Center College Park MD
308 PM EDT Tue Apr 27 2021

Areas affected...northeastern CO into southeastern WY, western NE
and northwestern KS

Concerning...Heavy rainfall...Flash flooding possible

Valid 271905Z - 272335Z

SUMMARY...Flash flooding will be possible later this afternoon
into the early evening across portions of northeastern CO into
southeastern WY and western NE/KS. Rainfall rates of 1-2 in/hr
combined with periods of training will lead to localized totals of
2-4 inches through 00Z.

DISCUSSION...Regional radar imagery at 1830Z showed scattered
convection in central and northern CO, near and east of I-25. The
storms were occurring within a post-frontal environment with
surface dewpoints in the mid-upper 40s and estimated MUCAPE of
500-1000 J/kg via the 18Z SPC mesoanalysis. Broad-scale lift and
increasing upper level diffluence was occurring across the central
High Plains out ahead of an elongated mid-level shortwave over
central NM, along with enhancement to vertical motion within the
left exit region of a 130 kt upper level jet max in place over the
southern High Plains.

Storm coverage is expected to increase and expand toward the east
through the rest of the afternoon into the early evening hours as
forcing for ascent continues to increase ahead of the shortwave
trough. A surface low to the northwest of SPD is forecast to
strengthen through 00Z as high pressure continues to build
southward over WY and NE. The increased pressure gradient should
allow upslope flow to increase in magnitude over northeastern CO
into adjacent WY, NE and KS. As this occurs, thunderstorms will
become more numerous, containing peak rainfall rates of 1-2 in/hr.
Brief periods of training and cell mergers will likely allow for
localized rainfall totals of 2-4 inches in a couple of locations
prior to 00Z. Given these rainfall rates and totals are in excess
of area flash flood guidance values, flash flooding will be
possible.

Otto

ATTN...WFO...BOU...CYS...GLD...LBF...PUB...

ATTN...RFC...ABRFC...MBRFC...NWC...

LAT...LON 41550390 41500279 40860181 39870193 39180282
39010464 39930510 40900516 41420466
$$
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AWUS01 KWNH 281751
FFGMPD
KYZ000-ILZ000-MOZ000-ARZ000-282347-

Mesoscale Precipitation Discussion 0124
NWS Weather Prediction Center College Park MD
148 PM EDT Wed Apr 28 2021

Areas affected...Northeastern Arkansas, Southeastern Missouri, Far
Southwestern Illinois

Concerning...Heavy rainfall...Flash flooding possible

Valid 281747Z - 282347Z

SUMMARY...Rainfall rates of 1-2 in/hr will continue to pose a
localized flash flood risk through late afternoon across portions
of northeastern AR, southeastern MO, and far southwestern IL.

DISCUSSION...

Bands and clusters of heavy showers and thunderstorms have
produced 1-3 inches of rain across portions of southeastern
Missouri into northeastern Arkansas over the last several hours.
Moisture influxes continuing into these areas combine with
elevated precipitable water values, areas of boundary layer
moisture convergence, and upper divergence maxima to support and
sustain thunderstorms capable of producing heavy to excessive
rainfall.

The hi-res models indicate bands of 2-4 inches of rain possible in
the 6 hour period through 00z. There is general agreement on the
areas impacted but the bands don't overlap well for a 6 hour
forecast.

The depicted risk contour is where recent rains have lowered flash
flood guidance values to less than one inch in 3 hours.
The 15z RAP indicates precipitable water values in excess of 1.75
inches through this region, as well as the 850 mb jet increasing
to 30-40 kts.

The 12z HREF shows a greater than 50 percent probability of an
additional inch of rainfall over the next 3-6 hours ending at 00z.
Where these heavy rains occur, localized flash flooding is
possible. Isolated maxima of 4 inches are possible.

Churchill/Bann

ATTN...WFO...LSX...LZK...MEG...PAH...SGF...

ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC...

LAT...LON 38328879 37108912 35669140 36249280 37589219
$$
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AWUS01 KWNH 011758
FFGMPD
TXZ000-012355-

Mesoscale Precipitation Discussion 0137
NWS Weather Prediction Center College Park MD
157 PM EDT Sat May 01 2021

Areas affected...South-central TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 011756Z - 012355Z

Summary...Thunderstorms producing heavy rainfall are expected to
continue to develop during the afternoon hours. Additional
amounts of 2-4 inches are expected, with flash flooding possible.

Discussion...As a slow-moving closed low remains centered near the
Big Bend, mid-level energy lifting north into Texas, along with
favorable upper jet forcing, is supporting an area of enhanced
ascent centered south-central Texas. At 17Z, observations
indicated a deepening surface wave moving northeast toward
Pleasonton (KPEZ). An initial line of convection, with radar
indicated rainfall rates of up 2 in/hr, is continuing to move
progressively east ahead of the low. However, as 20-30 kt
southerly low level winds support a period of sustained moisture
transport and increasing instability, expect convection to
increase in coverage with redevelopment to the south within the
highlighted region. For the 6-hr period ending at 23Z, recent
runs of the HRRR have been fairly consistent in showing locally
heavy amounts of 2-4 inches within the highlighted area. Overall,
the HRRR has been a little farther south and east and is more
preferred than the HREFmean given the deeper moisture and better
instability to the south. Heavy amounts may result in flash
flooding, especially within urbanized areas and areas recently
impacted by heavy rains.

Pereira

ATTN...WFO...CRP...EWX...FWD...HGX...SJT...

ATTN...RFC...WGRFC...NWC...

LAT...LON 31359866 31079716 29979667 28809695 27949752
27699776 27689825 28039852 28989870 29569912
29870025 30700034

$$
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AWUS01 KWNH 111724
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-112323-

Mesoscale Precipitation Discussion 0171
NWS Weather Prediction Center College Park MD
123 PM EDT Tue May 11 2021

Areas affected...Eastern Texas...Northwest Louisiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 111723Z - 112323Z

Summary...Scattered to widespread thunderstorms this afternoon
will be capable of producing heavy rainfall and could lead to
flash flooding.

Discussion...Visible satellite early this afternoon shows clearing
pocket developing across portions of eastern Texas and
western/northwest Louisiana while a surface analysis depicts a
boundary inching northward. Water vapor imagery shows a weak
shortwave trough moving through Texas. The environment ahead of
this approaching shortwave is warm and unstable with the mid 70
dewpoints in place contributing to the 2500 J/kg MLCAPE in the
latest mesoanalysis. PWs are above normal in the 1.5-1.7" range.
The combination of the low level convergence with the nearby front
and the large/broad upper divergence ahead of the approaching wave
will the lift needed to initiate convection this afternoon.
Upstream more organized thunderstorms are expected to fill into
the area as well leading to multiple boundary interactions and
cell mergers.

Forecast confidence isn't high on how the scenario will evolve but
the latest thinking and favored hi-res guidance is for the more
discrete cells in the warm sector to grow upscale and more
organized ahead of the line coming in from the west. Some
backbuilding or repeating rounds will be possible. The environment
supports some hourly totals near 2" though as cold pool processes
take over, there should be a decent forward motion to the line
segments later this afternoon which may limit the residence time
for heavy rainfall over any particular location. Portons of the
area have been running above normal precipitation departures with
soil moisture in the 0-40 cm layer above 80-90 percent. As a
result, some instances of flash flooding will be possible.

Taylor

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 33719599 33609405 32879301 31719332 30659493
30399709 31319832 33059734
$$
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AWUS01 KWNH 152252
FFGMPD
TXZ000-160300-

Mesoscale Precipitation Discussion 0176
NWS Weather Prediction Center College Park MD
652 PM EDT Sat May 15 2021

Areas affected...South Texas...

Concerning...Heavy rainfall...Flash flooding likely

Valid 152250Z - 160300Z

SUMMARY...Efficient rainfall thunderstorm cluster.

DISCUSSION...Cluster of thunderstorms at the confluent western
edge of trailing mid-level trough from exiting shortwave toward
the northeast continues to maintain with recent development.
GOES-E IR shows overshooting tops occasionally cycling colder than
-70C and regional RADARs denote rates in excess of 3"/hr.
Goes-Visible and CRP VWP denote solid streamers coming off the
Western Gulf with deep southeasterly flow of 20-30kts through the inflow/entrainment layer of 925-8H. RAP analysis TPW suggests
inflow values of 1.75", though CIRA Layer PW, particularly
surface-85H and 85-7H are within a tight gradient along the upwind
edge of the complex. This supports the south to south-southeast
propagation of the complex and additional cells over the past few
hours, counter to slacking mean steering flow. As such, there is
solid evidence to suggest the potential for long duration of
highly efficient downdrafts, though slightly displaced from
inflow/updrafts to maintain for the next few hours. On average
rates of 2"/hr are expected though as small surges occur, the
potential to 3"+ rates. As such potential for 3-5" totals
inducing flash flooding may occur, particularly in the next hour
or two before inflow is expected to slacken (per RAP/HRRR).

Gallina

ATTN...WFO...CRP...EWX...

ATTN...RFC...WGRFC...NWC...

LAT...LON 28949773 28759724 28329701 27729760 27709842
28059903 28529906 28819837
$$
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AWUS01 KWNH 171640
FFGMPD
LAZ000-TXZ000-172300-

Mesoscale Precipitation Discussion 0191
NWS Weather Prediction Center College Park MD
1240 PM EDT Mon May 17 2021

Areas affected...Far Southeast TX...Far Southwest LA

Concerning...Heavy rainfall...Flash flooding likely

Valid 171636Z - 172300Z

Summary...Areas of flash flooding will be likely through the
afternoon across portions of far southeast Texas and southwest
Louisiana. Highly efficient hourly rainfall rates of 2-3" will
allow for additional localized accumulations of 3-6 inches.

Discussion...Flash flooding is currently ongoing midday across
portions of the Sabine River basin, including across the Beaumont
metropolitan area. A nearly stationary area of surface moisture
convergence has allowed for periodic episodes of deep convection,
producing large swaths of 4-8 inches of precipitation over the
past 6 hours (per MRMS QPE products). These radar estimations
appear to be reasonably accurate with little indication of hail
contamination via analysis of dual-pol radar components. The
Beaumont/Port Arthur Regional Airport (KBPT) measured nearly 7
inches of rain in the past 6 hours, which corroborates MRMS
dual-pol driven radar estimates. The latest radar trends and
hi-res CAM guidance suggest that episodes of heavy precipitation
will continue over this region over the next several hours,
propagating westward toward the Houston metro along with an
approaching, and potentially stalling, outflow boundary from North
Texas.

The aforementioned eastern portions of the outlined area (from
Lake Charles to Beaumont) will continue to see flash flooding with
a large area of 3-hr FFG values of 2 inches or less. Further west
where new convection propagates (from the Houston metro westward),
FFG ranges from 3-5 inches. Deep convection will continue to be
capable of 2-3" per hour rainfall rates, supporting localized FFG
exceedance in only a couple hours where convection is able to
repeat/train. Some training of convection does appear likely, as
an outflow boundary from North TX gradually stalls out over the
outlined area, providing a focal point for new convective
initiation amid a rapidly destabilizing air mass (SB CAPE rising
to 3000-4000 J/kg).

Churchill

ATTN...WFO...EWX...HGX...LCH...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 30889434 30839290 30679242 30269268 29819314
29799360 29799433 29649530 29409684 30559604
$$
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AWUS01 KWNH 181820
FFGMPD
ALZ000-MSZ000-LAZ000-182300-

Mesoscale Precipitation Discussion 0201
NWS Weather Prediction Center College Park MD
217 PM EDT Tue May 18 2021

Areas affected...Southeast LA...Southern MS...Southwest AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 181816Z - 182300Z

SUMMARY...Slow moving heavy showers and storms are likely during
the afternoon hours, and some episodes of flash flooding will be
possible with rainfall rates of 2 to 3 inches per hour with the
most persistent convection.

DISCUSSION...A remnant MCV currently north of Lake Ponchartrain is
clearly evident on both regional Doppler radars and GOES-16
visible satellite imagery. There has been a recent resurgence of
very slow moving convection near the circulation, and there have
been some reports of 3 inch/hour rainfall rates as this band
recently passed through portions of the Interstate 12 corridor.
These showers are taking advantage of highly efficient warm cloud
processes. A secondary band of convection will likely develop
across southeast Mississippi as an inflow band to the MCV
circulation, with north-south oriented training within this
corridor.

The latest HREF probabilities have a rather clear signal for
localized 2+ inch/hour rates through 6 pm local time, approaching
50 percent around 3 pm. The latest HRRR seems to have a
reasonable depiction of ongoing convection, and this model is
suggesting the potential for 2-4 inch totals during the outlook
period. Parts of southeast Louisiana and south-central
Mississippi have already picked up at least an inch of rain over
the past 24 hours, and these areas are more vulnerable to heavy
rain this afternoon.

Hamrick

ATTN...WFO...JAN...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 32909003 32868981 32568948 32398917 32338889
32158857 31648829 30988798 30448796 30228818
30298870 30648894 30808910 30838952 30638995
30659027 30829061 31249075 31869056 32289031
32639022

$$
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AWUS01 KWNH 181912
FFGMPD
TXZ000-190100-

Mesoscale Precipitation Discussion 0202
NWS Weather Prediction Center College Park MD
311 PM EDT Tue May 18 2021

Areas affected...Portions of South Texas and Central Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 181911Z - 190100Z

Summary...The threat of flash flooding will persist across
portions of South Texas and Central Texas during the afternoon and
early evening as cells build into a moist and unstable atmosphere
where flash flood guidance values have been lowered recently.

Discussion...Thunderstorms capable of producing downpours should
become more numerous this afternoon and evening as low level
outflow from this morning's MCS pushes southward into a region
where ML Cape values of 3500 to 5000 J per kg are expected by 21Z.
In addition, 1-hour and 3-hour flash flood guidance values have
lowered into the 1.5 to 2 inch range by recent rainfall. An
outflow boundary associated with the convective complex earlier
this morning will help focus a moisture flux convergence max which
gradually pushes south and east during the afternoon and early
evening.

Latest radar trends and hi-res CAM guidance has started to show
intensification of cells moving out of Kendall and Medina
counties. These cells will move into a region where precipitable
water values increase to around 1.5 inches and where the RAP runs
show MLCAPE building to more than 5000 J per kg. This suggests
that some 1.5 to 2.5 inch per hour rainfall rates could occur.
The lowered flash flood guidance, in part, reflects the recent
rainfall (also shown in the NASA SPoRT 0-40 cm soil moisture
percentile product) as well as the terrain of the Hill Country.

Given the antecedent conditions, instances of flash flooding are
possible.

Bann

ATTN...WFO...CRP...EWX...FWD...HGX...

ATTN...RFC...WGRFC...NWC...

LAT...LON 31029697 30149614 29659592 29039653 28759710
28209784 27809842 27819896 27919969 28189991
28789997 28989948 29629882 30279823
$$
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AWUS01 KWNH 192044
FFGMPD
LAZ000-ARZ000-200130-

Mesoscale Precipitation Discussion 0209
NWS Weather Prediction Center College Park MD
443 PM EDT Wed May 19 2021

Areas affected...Arkansas

Concerning...Heavy rainfall...Flash flooding possible

Valid 192042Z - 200130Z

Summary...Flash flooding is possible over portions of Arkansas
during the late afternoon and early evening as broad south to
southeast flow continues to draw moisture into the region.
Western and central portions of Arkansas received 2 to 5 inches of
rain last night/early this morning....making it more susceptible
to additional flooding concerns this evening.

Discussion...Convection over parts of Louisiana and Arkansas was
becoming more numerous and more capable of producing locally heavy rainfall..especially across the central portion of the state where
storms were developing on the nose of a 2.00 inch precipitable
water plume and where southeasterly flow was tapping an airmass
with MUCAPE values of 1000 to 1500 J per kg. Atfernoon VAD Wind
Profiles across the region show that the flow has backed and
accelerated to 25-35 kts at 850 mb since the 12Z soundings...and
that flow has been providing plenty of additional moisture
transport into the region. Flash flooding is possible wherever
convective activity occurs over areas of central and western
Arkansas which received 2 to 5 inches of rain last night/early
this morning.

Present indications are that the probability of rainfall exceeding
1 inch per hour should diminish shortly after 20/00Z as the lower
atmosphere begins to stabilize.

Bann

ATTN...WFO...JAN...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 36179213 35419128 33469137 32799252 33259324
34329346 35429333 35889299
$$
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AWUS01 KWNH 201757
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-202355-

Mesoscale Precipitation Discussion 0216
NWS Weather Prediction Center College Park MD
156 PM EDT Thu May 20 2021

Areas affected...Louisiana...Far Southeast Arkansas...Far Eastern
Texas

Concerning...Heavy rainfall...Flash flooding likely

Valid 201755Z - 202355Z

Summary...Flash flooding is likely this afternoon across much of
Louisiana, far southeastern Arkansas, and far eastern Texas with
rainfall rates increasing to 2-3"/hr. Additional accumulations are
expected to reach 3-6" where showers and thunderstorms train.

Discussion...Convective activity along the LA Gulf coast is
expected to increase this afternoon as SB CAPE ramps up to
1000-2000 J/kg amid peak solar insolation. An exceptional moist
air mass remains in place with PWATs ranging from 1.75-2.00
inches, at or above the 90th climatological percentile for
surrounding WFOs. Efficient low-level moisture transport from the
Gulf will continue with a 25-35 kt 850 mb jet over the region.
Mid- to upper-level forcing continues to be the limiting factor at
play today, but the highly moist and unstable air mass within a
corridor of persistent low-level confluence will keep excessive
rain potential elevated.

The latest radar trends and hi-res CAM guidance suggest that the
ongoing convection across southeastern Louisiana this morning will
begin to shift westward into west-central Louisiana and
neighboring portions of Arkansas and Texas. As instability
increases, expect hourly rainfall rates to increase to the
2-3"/hour range. Training of these rates will allow for 3-6"
totals across an already highly saturated area. 3-hr FFG values
are less than 3 inches across the highlighted area, and even less
than 2 inches across much of Sabine River basin (from Port Arthur,
TX to near Shreveport, LA). Therefore hydrologic sensitivity is
quite high, as NASA SPoRT 0-40 cm soil moisture anomalies exceed
the 90th percentile.

Churchill

ATTN...WFO...JAN...LCH...LIX...SHV...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 33519411 33099197 31289109 30149019 28999106
29689384 31529419
$$
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AWUS01 KWNH 201810
FFGMPD
MOZ000-IAZ000-KSZ000-NEZ000-210009-

Mesoscale Precipitation Discussion 0217
NWS Weather Prediction Center College Park MD
209 PM EDT Thu May 20 2021

Areas affected...Eastern Kansas...Northwest Missouri

Concerning...Heavy rainfall...Flash flooding possible

Valid 201809Z - 210009Z

Summary...Locally heavy rainfall this afternoon could lead to
instances of flash flooding across portions of eastern Kansas.
Rainfall totals up to 2" will be possible.

Discussion...Within an area of broad upper divergence from a
shortwave trough moving through Plains and another wave embedded
with the deeper tropical plume from the south, a remnant MCV has
been producing widespread rainfall across portions of eastern
Oklahoma and southeastern Kansas this morning into the early
afternoon. This area is within a plume of highly anomalous
moisture with the latest blended TPW products showing 1.6-1.8"
which is about 2 standard deviations above normal. Widespread
cloud cover has limited better SBCAPE from building but the most
recent mesoanalysis suggests upwards of 500 J/kg exists and within
any clearing pockets that do develop this afternoon, some
increases are possible.

The converging low level flow ahead of the approaching remnant MCV
coinciding with peak heating should allow for an upscale in
convective trends this afternoon into the early evening hours.
Storms should generally track northward and this is likely to fall
across eastern Kansas and perhaps extreme western Missouri. The
most recent guidance suggests 1.5-2" with some local 2-3" amounts
will be possible. Over the last 24 hours, 2 to locally 3"+ fell
across portions of eastern/southeastern Kansas. As such, the
latest FFGs are lowered (1-hr < 1.5") and the NASA SpoRT soil
moisture shows some areas of 90+ percent saturation in the 0-100
cm layer. If the additional rainfall were to track over this same
areas, then some instances of flash flooding will be possible.

Taylor

ATTN...WFO...EAX...ICT...OAX...SGF...TOP...

ATTN...RFC...ABRFC...MBRFC...NWC...

LAT...LON 40719530 40149461 38289458 37429451 37099551
37319625 38259640 39959609
$$
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AWUS01 KWNH 231927
FFGMPD
MIZ000-240126-

Mesoscale Precipitation Discussion 0224
NWS Weather Prediction Center College Park MD
326 PM EDT Sun May 23 2021

Areas affected...portions of Michigan

Concerning...Heavy rainfall...Flash flooding possible

Valid 231926Z - 240126Z

Summary...A few areas in central Michigan may experience enough
rain to exceed flash flood guidance over the next few hours as a
front moves southward through the discussion area.

Discussion...Recent radar imagery indicates a band of scattered
showers and thunderstorms in the general vicinity of Reed
City/Mount Pleasant, Michigan. The storms have recently developed
along a southwestward-moving cold front that generally extends
from near MTC to near MBL, and although the front appears to have
undercut some of the convection, radar estimates of 1-2
inch-per-hour rainfall rates beneath heavier cores have been
observed. The nature of the boundary and orientation of
convection generally parallel to 30-40 knot 300-500mb flow aloft
suggests that training of convection may occur, with roughly
1000-1500 J/kg MUCAPE along and south of the convection and
sustained (though weak) convergence along the boundary also
supporting this notion. Localized areas of rainfall totals near 3
inches appear possible with this scenario, which would exceed
areal flash flood guidance.

Over time, the general regime (with localized training of
convection) will migrate southward/south-southeastward through
downstream areas of lower Michigan and perhaps northwestern Ohio
through tonight. Locally heavy rainfall will also be possible in
these areas.

Cook

ATTN...WFO...APX...DTX...GRR...

ATTN...RFC...NCRFC...NWC...

LAT...LON 44248615 44218542 43958433 43368359 42648339
42198361 42118434 42638534 43028578 43288604
43628631
$$
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AWUS01 KWNH 232046
FFGMPD
TXZ000-240000-

Mesoscale Precipitation Discussion 0225
NWS Weather Prediction Center College Park MD
445 PM EDT Sun May 23 2021

Areas affected...south/southeast Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 232039Z - 240000Z

Summary...A persistent south-southeasterly flow regime will
continue to support showers and a few thunderstorms across the
discussion area this evening along with a risk of flash flooding.

Discussion...A persistent, deep south-southeasterly flow regime
continues between the southwestern periphery of a mid/upper ridge
centered over the Mid-South and a weak mid-level vort max centered
about 100 mi E of Brownsville. The flow pattern is continuing to
support a very moist, weakly buoyant airmass across the discussion
area with 2-2.2 inch PW values and 1000-1500 J/kg MUCAPE. The
airmass is weakly capped, and subtle lift associated with the
mid-level vort max and weak/subtle boundary layer confluence
continues to support areas of showers with embedded thunderstorms.
A couple of bands of heavier precipitation exist from near
Gonzales to Victoria, Texas and across the western Houston Metro
area, with enhanced rainfall rates of near 1-2 inches per hour
noted in the western-most band near Gonzales.

This persistent precipitation regime is expected to continue for
at least the next 3 hours or so as southeasterly low-level flow
maintains very moist low-level air and the mid-level vort max is
very slow to move. This will allow for occasional/isolated bands
of heavier precipitation to fall in areas that have received
abundant rainfall over the past week - exceeding 15 inches in a
few spots. The precipitation is resulting in wet soils and
correspondingly low flash flood guidance as a result (as low as 1
inch-per-hour thresholds near PSX/VCT). Additionally, showers and
isolated thunderstorms currently offshore (east of the mid-level
vort max) will migrate inland into the discussion area over the
next 2-3 hours. Most CAMs suggest a downtick in precipitation
rates after around 00Z or so, and the risk of additional flash
flooding will be re-evaluated around that time.

ATTN...WFO...CRP...EWX...FWD...HGX...

ATTN...RFC...WGRFC...NWC...

LAT...LON 30819714 30719608 30209510 29629472 29049495
28459619 28379715 28799794 29199814 29829821
30279811 30599783
$$
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AWUS01 KWNH 251918
FFGMPD
TXZ000-260115-

Mesoscale Precipitation Discussion 0236
NWS Weather Prediction Center College Park MD
317 PM EDT Tue May 25 2021

Areas affected...Eastern TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 251915Z - 260115Z

SUMMARY...Showers and thunderstorms with heavy rainfall rates may
pose some flash flood threat over the next few hours.

DISCUSSION...The latest radar imagery shows a long-lived MCS now
bowing into areas of eastern TX. The airmass out ahead of this
over the broader southeast TX coastal plain is quite moist and
unstable with PWs of 1.8 to 2 inches and MLCAPE values locally
over 2000 j/kg. Meanwhile, a southerly low-level jet of 30 kts is
in place ahead of the MCS.

This favorable thermodynamic environment downstream of the MCS
suggests the ongoing activity will continue to expand off to the
east with some upside potential to expand in coverage and gain
greater convective organization given the additional
destabilization of the boundary layer that is expected over the
next couple of hours due to solar insolation.

Dual-pol radar QPE has already been suggesting some 1.5+ inch/hr
rainfall rates, and these rates should continue within the
stronger cells over the next few hours given the efficient
moisture transport pattern. The radar imagery also shows scattered
heavy showers and thunderstorms developing ahead of the main
complex within the moist/unstable low-level flow with locally
enhanced rain rates.

Over the next few hours, the southern portion of the long-lived
MCS may begin to slow its advance off to the east and may tend to
become oriented more southwest/northeast in nature such that
individual cells may begin to train over the same area. This
coupled with some cell-merger potential will tend to increase the
threat for some excessive rainfall totals going through the
late-afternoon and early evening hours.

The latest HRRR guidance suggests at least locally 3 to 4+ inch
rainfall totals going through 00Z. Given the wet antecedent
conditions, and heavy short-term rainfall rate potential, there
will be at least some concern for flash flooding.

Orrison

ATTN...WFO...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON 31999435 31759401 31279389 30589444 30069531
30079603 30289639 30439657 30589667 30799673
30999656 31409561 31949499
$$
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AWUS01 KWNH 271708
FFGMPD
MOZ000-ARZ000-OKZ000-KSZ000-272305-

Mesoscale Precipitation Discussion 0245
NWS Weather Prediction Center College Park MD
105 PM EDT Thu May 27 2021

Areas affected...Northeast OK...Southeast KS...Southwest MO...Far
Northwest AR

Concerning...Heavy rainfall...Flash flooding likely

Valid 271705Z - 272305Z

Summary...Scattered areas of flash flooding will be likely across
portions of the Southern Plains this afternoon as deep convection
blossoms within a broad unstable warm sector. Hourly rainfall
rates of 2-3" are expected with 6-hr localized accumulations of
4-6 inches possible where convection trains.

Discussion...A broad warm sector characterized by MUCAPE of
2000-4000 J/kg, PWATs of 1.6-1.9 inches, and significant deep
layer moisture convergence will foster rapid upscale growth of
convection across the Southern Plains this afternoon as a potent
mid-level shortwave digs southeastward from the Northern Plains.
Semi-discrete thunderstorms will initially be relatively slow
(15-20 kts) with 2-3"/hr rainfall rates quickly saturating soils.
Much of the highlighted area is already in the 60-90th percentile
of 0-40 cm soil moisture (via NASA SPoRT Land Info System data),
indicating somewhat vulnerable antecedent hydrologic conditions.

Given that the latest high-res CAM guidance (including the HRRR)
has continued to handle convective trends rather poorly,
confidence in any targeted specific area is somewhat low. Where repeating/training of convection can occur 2-3" hourly rates will
rapidly translate to localized totals of 4-6 inches. Some
preference is given to northeastern Oklahoma to realize the
highest rainfall totals, but this area is also where 6-hr FFG is
the highest (3-5 inches). While southeast Kansas in particular has
the lowest FFG (2-4 inches), less repeating of convection is
likely as the advancing cold front cuts off avaliable instability.
That said, the combonation of a highly favorable mesoscale
enviorment and relatively poor hydrologic conditions make
localized flash flooding likely over the broader region.

Churchill

ATTN...WFO...EAX...ICT...LSX...LZK...OUN...SGF...TOP...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NWC...

LAT...LON 39059479 38889350 38389241 36129320 35379462
35469789 37119753 37999677 38519579
$$
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AWUS01 KWNH 311322
FFGMPD
TXZ000-311800-

Mesoscale Precipitation Discussion 0255
NWS Weather Prediction Center College Park MD
922 AM EDT Mon May 31 2021

Areas affected...North - Central Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 311321Z - 311800Z

Summary...Showers and thunderstorms developing along a cold front
will increase in coverage and intensity through late morning.
Rainfall rates are likely to exceed 2"/hr by the afternoon, and
training of these cells to the east could produce 2-4" of
rainfall. Flash flooding is possible.

Discussion...GOES-E IR imagery and the regional radar mosaic
depict cooling cloud tops and intensifying reflectivity indicative
of deepening convective development this morning. This convection
is blossoming along a moisture convergence axis associated with a
cold front that is being driven slowly southward on cyclonic flow
behind an MCV/surface low lifting through Oklahoma. This front is
sagging into a region of anomalous PWs and strong instability,
which will support continued thunderstorms, with both coverage and
intensity likely to build through early afternoon as the front
stalls across the region.

PWs as sampled by GPS observations and measured by 12Z U/A
soundings are 1.2-1.5", with 1.47" measured at KMAF. This is well
above the climatological 90th percentile, and is leading to
efficient rainfall production. The southerly LLJ is still analyzed
by VWPs and the RAP to be around 30 kts, which is impinging nearly
orthogonally into this front to drive ascent. However, this LLJ is
likely to veer and weaken over the next few hours. Despite the
less favorable LLJ position, this loss of ascent will be somewhat
offset by increasing instability through daytime heating and
continued mid-level lapse rates near moist adiabatic rates of
7C/km within a broad positively tilted trough. The combination of
the favorable thermodynamics and forcing through mid-level
impulses rotating through the flow is likely to drive waves of
thunderstorms today.

As the environment becomes more supportive, the HREF probabilities
indicate an increasingly likelihood for 2-3"/hr rain rates along
this boundary. The high-res guidance is struggling to handle the
ongoing convection which is leading to a wide variation in model
solutions over the next several hours. However, it is likely that
convection will develop and train over nearly the same areas along
the front due to propagation vectors and mean 0-6km winds aligned
to the boundary. Some of this area has received 2-3" of rainfall
this morning, leading to locally reduced FFG and higher soil
moisture conducive to rapid runoff and possible flash flooding.
While the highest HREF exceedance probabilities are progged later
today, these training storms, especially if they occur over the
pre-conditioned soils, could lead to flash flooding.

Weiss

ATTN...WFO...FWD...LUB...MAF...OUN...SJT...

ATTN...RFC...ABRFC...WGRFC...NWC...

LAT...LON 34190066 34060000 34009936 33729888 33479873
33089883 32779924 32599997 32420054 32300123
32220193 32250261 32460287 32930296 33290288
33690275 34070212
$$
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AWUS01 KWNH 311922
FFGMPD
COZ000-NMZ000-010120-

Mesoscale Precipitation Discussion 0257
NWS Weather Prediction Center College Park MD
321 PM EDT Mon May 31 2021

Areas affected...Sangre De Cristos

Concerning...Heavy rainfall...Flash flooding possible

Valid 311920Z - 010120Z

Summary...Scattered showers and thunderstorms will develop along
the high terrain and move slowly eastward through the afternoon.
Rain rates may reach 1"/hr at times and produce 1-2" of rainfall
with locally higher amounts. Flash flooding is possible,
especially within any sensitive burn scars.

Discussion...GOES-E visible imagery this afternoon indicates
rapidly building TCu and Cb across the terrain of CO and NM
including the San Juans and Sangre De Cristos. These blossoming
clouds are reflective of strengthening thunderstorms that are
evident on local radar in an increasingly favorable thermodynamic
environment. The 12Z U/A sounding at KABQ measured a PW of 0.78",
which is above the 90th percentile for the date, with more than
1000 J/kg of MUCape thanks to steep 700-500mb lapse rates. These
mid-level lapse rates will remain steep as a positively tilted
trough sinks slowly southward atop the region, with embedded weak
impulses providing additional ascent.

Through the afternoon and during peak heating, thunderstorms are
likely to become scattered to numerous, especially in the higher
terrain. Weak 0-6km bulk shear of 20 kts or less should preclude
much in the way of storm organization, leading to primarily pulse
convective mode. Despite this, PWs +1-1.5 standard deviations
above the climatological mean pooled with ample instability due to
the aforementioned steep lapse rates aloft and diurnal heating
will produce an environment favorable for heavy rain rates.
Additionally, a weak shortwave progged to drop southward within
the mean trough could also enhance ascent. Recent HREF
probabilities indicate a 20-30% chance for 1"/hr or greater rain
rates, and with mean cloud layer winds generally 10 kts or less,
this could quickly produce 1-2" of rainfall with locally higher
amounts. As storms eject slowly eastward towards the High Plains
they will encounter greater stability, suggesting the flash flood
threat should remain tied to the terrain this aftn.

Despite a lack of organization and the scattered nature of this
convection, the slow moving heavy rain producers could produce
isolated flash flooding. The HREF exceedance probabilities for
3-hrs are modest, generally 10-20%, with the highest chances
confined to a narrow corridor of lower FFG along the Sangre De
Cristos where 14-day rainfall has been as high as 300% of normal.
However, these probabilities likely do not reflect the more
sensitive nature of recent burn scars which could flash flood in
even less intense rainfall. Isolated flash flooding is possible,
but is most likely should these rain rates impact any of the burn
scars.


Weiss/Churchill

ATTN...WFO...ABQ...BOU...GJT...PUB...

ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC...

LAT...LON 39330492 39230437 39010415 38820432 38730456
38590479 38210490 37910478 37600452 37240448
36710459 36230466 35860485 35600526 35440568
35450615 35520662 35690695 36020710 36370695
36800684 37210697 37550696 37920690 38740650
39080613 39170588
$$
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AWUS01 KWNH 011904
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-012300-

Mesoscale Precipitation Discussion 0263
NWS Weather Prediction Center College Park MD
303 PM EDT Tue Jun 01 2021

Areas affected...Eastern TX...Southern AR...North/Central LA

Concerning...Heavy rainfall...Flash flooding possible

Valid 011900Z - 012300Z

Summary...Showers and thunderstorms will continue to blossom
across eastern TX into southern AR and much of LA through the
afternoon. Some of this activity will be slow moving and with the
potential for training over the same areas. Therefore, rain rates
in excess of 2 inches/hour are possible with areal average
rainfall of 2-4+ inches possible through the next six hours.
Antecedent conditions combined with high resolution model signals
suggest flash flooding is possible.

Discussion...A mid/upper level trough across the central U.S. will
continue to provide modest divergence aloft. This combined with
shortwave activity (including an eastward advancing MCV in
northeastern TX) will lead to large scale forcing for ascent. In
response, rich Gulf moisture will be pulled north into eastern TX
and the Lower MS Valley region ahead of a stationary surface
boundary. As a result, precipitable water values of 1.5-1.75
inches will expand east and increase with strong WAA. Despite
morning cloud debris from earlier convection, MUCAPE has already
climbed above 2000 J/kg with additional destabilization expected
over the next several hours. Given these factors, anticipate
convection will continue to develop and blossom within this
region. Based on the propagation vectors and mean wind,
anticipate convection to be slow moving initially with the
potential for brief training. It should also be noted that with
weak shear of around 25 knots, highly organized convection is not
expected but possible across portions of eastern LA by later this
afternoon. According to high resolution guidance, rain rates may
exceed 2 inches/hour with areal average precipitation of 2-4+
inches within the next six hours. This is supported by the higher
HREF probabilities.

While flash flood guidance values within this region are fairly
high (3-5 inches in 3 hours), portions of the ArkLaTex region has
observed above normal precipitation over the past week along with
slightly above normal soil moisture within the scalloped region.
Therefore, scattered flash flooding may occur.

Pagano

ATTN...WFO...HGX...JAN...LCH...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34449293 33279115 31199173 30109333 30069533
30649632 31599495 33329448
$$
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AWUS01 KWNH 081557
FFGMPD
MAZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-082156-

Mesoscale Precipitation Discussion 0300
NWS Weather Prediction Center College Park MD
1157 AM EDT Tue Jun 08 2021

Areas affected...northeastern Pennsylvania into southern New York
State

Concerning...Heavy rainfall...Flash flooding possible

Valid 081556Z - 082156Z

Summary...Slow-moving storms will pose a risk for isolated flash
flooding through the afternoon and early evening in and near the
discussion area.

Discussion...A slow-moving cluster of convection has evolved in
northeastern Pennsylvania over the past hour or so, with areas of
towering cumulus across much of the discussion area from
southeastern Pennsylvania to western Massachusetts. The storms
are in an environment characterized by weak, but westerly vertical
shear and very strong instability (as high as 4000 J/kg SBCAPE in
areas downstream of ongoing storms). The pre-convective airmass
is quite moist also, with PW values of 1.6 to 1.9 inch areawide.
Lift from an approaching shortwave trough across central PA/NY and
weak/subtle boundary layer confluence was also providing ascent
aloft for thunderstorm development.

Latest observations/guidance suggests that this mainly diurnally
driven convective activity will continue to expand in coverage
this afternoon. Local rainfall rates of 1-2 inches per hour have
already been observed beneath convective cores, and this will
expand in coverage with time - especially as storms form mature
cold pools and propagate slowly eastward. Flash flood guidance
values are in the 0.75-1.5 inch-per-hour range, which should be
easily exceeded beneath heavier convective cores/clusters. The
threat should wane some after sunset with loss of
heating/surface-based instability.

Cook

ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI...

ATTN...RFC...MARFC...NERFC...NWC...

LAT...LON 43057325 42817261 42157246 41557285 40927380
40337472 40037588 40107668 40307712 40607717
42347608 42697525 43017412
$$
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AWUS01 KWNH 081646
FFGMPD
NDZ000-082244-

Mesoscale Precipitation Discussion 0301
NWS Weather Prediction Center College Park MD
1245 PM EDT Tue Jun 08 2021

Areas affected...North Dakota

Concerning...Heavy rainfall...Flash flooding possible

Valid 081644Z - 082244Z

Summary...Areas of flash flooding are expected to continue through
the afternoon across the discussion area.

Discussion...A complex convective evolution continues to unfold
across central North Dakota, with slow westward propagation of
convection associated with storms along a synoptic warm front now
nearly stationary just east of the Bismarck area. One complex in
particular (centered over Kidder County) is nearly stationary
while producing estimated 1-3 inches of rainfall in an hour.
These rainfall values will readily exceed the 1.5-2.5
inch-per-hour flash flood guidance thresholds across the region,
promoting a continued risk of flash flooding there.

The complex evolution lends some uncertainty with respect to
evolution of the convection over the next 6 hours or so. The
presence of a weak shortwave trough just west of the region and
convergence along the warm frontal zone will continue to foster
development of new convection near the initial complex and these
cells may also move slowly northward, backbuild, and/or stall.
Additionally, as the warm front lifts slowly northward, the axis
of focus for development may also shift northward (as suggested by
the latest runs of the HRRR), with potential for heavy rainfall
and isolated flash flooding extending northward/northwestward over
the next 3-6 hours or so. Flash flood guidance values are
slightly lower in western and northern North Dakota (around 1"/hr)
compared to near Bismarck (1.5-2.5"/hr). It is possible that
stronger convection (with heavier rainfall) remains rooted closer
to the warm front through the afternoon where stronger
instability, lesser inhibition (in the 700-850mb layer), and more
focused surface convergence resides.

Cook

ATTN...WFO...BIS...FGF...

ATTN...RFC...MBRFC...NCRFC...NWC...

LAT...LON 48550059 48189930 47349867 46439904 46180027
46390191 46960272 47410284 48110253 48410182
$$
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AWUS01 KWNH 081911
FFGMPD
OHZ000-MIZ000-INZ000-082315-

Mesoscale Precipitation Discussion 0302
NWS Weather Prediction Center College Park MD
311 PM EDT Tue Jun 08 2021

Areas affected...Northwest OH...Northeast IND...Ext Southwest MI.

Concerning...Heavy rainfall...Flash flooding possible

Valid 081910Z - 082315Z

SUMMARY...Slow moving cells and deepening moisture profiles
support localized heavy rainfall and potential for flash
flooding...

DISCUSSION...GOES-E WV suite denotes older shortwave/closed low
feature over the Tri-State area of S MI/NW OH/NE IND. Given its
placement in the larger scale pattern, upper level flow is
favorable for solid diffluence to support the developed convection
in/east of the UL proper. CIRA LPW suite also denotes moisture
entering the low to middle profile of the cells to further enhance
the rainfall efficiency, resulting in 1.75 to 1.9" of total
moisture in the column. Entrainment with 15-20kts of flow through
85-7H brings rates to 2-2.25"/hr, though equally allows for slow
cell motions and with upstream inflow and upstream propagation to
further slow motions. Strongest overshooting top near Hancock
county, OH seems to be ideally situated for this combination of
favorable upper-level divergence to show signs of building back
against the flow slightly. Development is enhanced by solid low
level convergence along Lake enhanced boundaries intersecting with
the weak northward march of the higher Td air from the
Ohio/Mississippi Valleys.

While the area is generally below average in the longer terms...
there is lower FFG values across the area of concern which aligns
with with AHPS 2-week anomalies near to 200% of normal. Hourly
FFGs of 1-1.5" and 3hr values of 1.5-2.5" have solid potential to
be exceeded with these cores. But given the nature of the complex
overall coverage should be scattered in nature and will dissipate
with reducing instability into the evening. As such, flash
flooding is considered possible but local thunderstorms of 2-3"
totals in 1-2 hours or even sub-hourly per report near Vermilion.

Gallina

ATTN...WFO...CLE...DTX...ILN...IWX...

ATTN...RFC...NCRFC...OHRFC...NWC...

LAT...LON 42358328 41698290 41558155 41128142 40638193
40448272 40538339 40938435 41008536 41398551
41748465
$$
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AWUS01 KWNH 091505
FFGMPD
TNZ000-ALZ000-MSZ000-ARZ000-092102-

Mesoscale Precipitation Discussion 0312
NWS Weather Prediction Center College Park MD
1104 AM EDT Wed Jun 09 2021

Areas affected...northern Mississippi, eastern/southeastern
Arkansas, northwestern Alabama

Concerning...Heavy rainfall...Flash flooding likely

Valid 091502Z - 092102Z

Summary...Areas of flash flooding remain likely across the
discussion area through at least 21Z. Significant impacts are
expected given extreme antecedent rainfall over the past 24 hours.

Discussion...Recent radar mosaic imagery indicates several bands
of slow-moving/propagating convection across the discussion area -
particularly in eastern Arkansas, northern Mississippi (near
Oxford), and northern Alabama (northwest of Birmingham). The location/orientation of these bands isn't particularly surprising
given broadly confluent westerly/southwesterly 850mb flow
partially orthogonal to a weak low-level boundary from near Little
Rock to near Tupelo. The low-level flow was maintaining a moist,
destabilizing pre-convective airmass across the region
(characterized by 2-inch PW values, nearly 2000 J/kg MUCAPE, and
minimal convective inhibition). The moisture and instability was
promoting rainfall rates of up to 3 inches per hour beneath
heavier thunderstorm cores which easily exceed FFG thresholds in
the region - especially in eastern Arkansas and northern
Mississippi where widespread areas of 3-10 inches of rainfall were
observed yesterday. Impressive MRMS Flash responses have already
been noted this morning in east-central Arkansas and near Oxford,
Mississippi.

Though the general axes of convergence are less focused compared
to yesterday, models/observations generally suggest that bands of
heavy rainfall will continue to propagate slowly
eastward/east-southeastward resulting in very heavy rainfall and
additional accumulations of at least 2-4 inches (locally higher)
through 2030Z. Models also indicate initiation of convection
south of these bands, which isn't surprising given the strong
destabilization occurring there. Localized training of convection
is expected in this regime (which may already be materializing in
east-central Arkansas). Convective mergers may also allow for a
slow, more southward component to MCS motions during the period as
well, allowing for heavier precipitation to eventually shift
toward the US82 corridor in Mississippi. Each of the
aforementioned factors point to locally significant flash flooding
especially beneath heavier/training convection.

Cook

ATTN...WFO...BMX...HUN...JAN...LZK...MEG...OHX...

ATTN...RFC...ABRFC...LMRFC...SERFC...NWC...

LAT...LON 35068996 35018783 34828659 34608618 34118614
33568659 33268805 33139020 33109190 33399234
34059232 34689205 34949122
$$
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AWUS01 KWNH 091732
FFGMPD
NYZ000-PAZ000-WVZ000-OHZ000-092331-

Mesoscale Precipitation Discussion 0314
NWS Weather Prediction Center College Park MD
132 PM EDT Wed Jun 09 2021

Areas affected...Virginia, northern North Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 091731Z - 092331Z

Summary...Convection drifting slowly southward across the
discussion area could pose a very localized/isolated flash flood
risk through peak-heating hours..

Discussion...Satellite/lightning imagery indicates scattered
thunderstorms across the discussion area that were moving slowly south-southwestward. The cells were in an environment
characterized by very weak vertical wind shear (with northerly
flow around 10 knots or so from the surface to 300mb), moderate
instability (around 2000 J/kg MLCAPE), and PW values ranging from
1.3-1.7 inch. These conditions are conducive for brief heavy
downpours with as much as 1 inch per hour of rainfall in a few
spots. FFG values of around 1.5 inch-per-hour rainfall rates
(slightly lower in southern New York State and southwestern
Pennsylvania) suggest that a brief/isolated flash flood risk will
exist - particularly in areas where heavier rainfall occurs over
flood-prone or hydrophobic surfaces (i.e., urban areas and hilly
terrain). This risk should be mainly dirunally driven and lessen
after sunset.

Cook

ATTN...WFO...BGM...BUF...CLE...CTP...PBZ...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON 42317939 42297756 41927676 41567661 40907664
40347684 39847756 39977979 40688129 41208142
41688113
$$
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AWUS01 KWNH 091739
FFGMPD
NYZ000-PAZ000-WVZ000-OHZ000-092337-

Mesoscale Precipitation Discussion 0314...Corrected
NWS Weather Prediction Center College Park MD
138 PM EDT Wed Jun 09 2021

Corrected for Areas Affected Header

Areas affected...northeastern Ohio, Pennsylvania, and far southern
New York State.

Concerning...Heavy rainfall...Flash flooding possible

Valid 091737Z - 092337Z

Summary...Convection drifting slowly southward across the
discussion area could pose a very localized/isolated flash flood
risk through peak-heating hours..

Discussion...Satellite/lightning imagery indicates scattered
thunderstorms across the discussion area that were moving slowly south-southwestward. The cells were in an environment
characterized by very weak vertical wind shear (with northerly
flow around 10 knots or so from the surface to 300mb), moderate
instability (around 2000 J/kg MLCAPE), and PW values ranging from
1.3-1.7 inch. These conditions are conducive for brief heavy
downpours with as much as 1 inch per hour of rainfall in a few
spots. FFG values of around 1.5 inch-per-hour rainfall rates
(slightly lower in southern New York State and southwestern
Pennsylvania) suggest that a brief/isolated flash flood risk will
exist - particularly in areas where heavier rainfall occurs over
flood-prone or hydrophobic surfaces (i.e., urban areas and hilly
terrain). This risk should be mainly dirunally driven and lessen
after sunset.

Cook

ATTN...WFO...BGM...BUF...CLE...CTP...PBZ...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON 42317939 42297756 41927676 41567661 40907664
40347684 39847756 39977979 40688129 41208142
41688113
$$
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AWUS01 KWNH 101620
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-102215-

Mesoscale Precipitation Discussion 0321
NWS Weather Prediction Center College Park MD
1219 PM EDT Thu Jun 10 2021

Areas affected...portions of the northern Mid-Atlantic region

Concerning...Heavy rainfall...Flash flooding likely

Valid 101616Z - 102215Z

SUMMARY...Slow moving thunderstorms are expected to increase in
coverage across the northern Mid-Atlantic region this afternoon.
Rainfall rates of 1-2 in/hr will be common, but locally higher
rates can not be ruled out.

DISCUSSION...Visible satellite imagery through 1545Z showed an
expanding cumulus field within an otherwise mostly clear
environment across the Delmarva Peninsula into MD and southeastern
PA. A few showers and thunderstorms have also popped up on
regional radar imagery over northern Delaware Bay and along the
Catocin Mountains of northern MD into the Appalachian chain of
southern PA. PWATs within the pre-convective environment are 1.7
to 2.0 inches and 850-200 mb mean-layer flow is very weak across
the entire region at less than 10 kt, which will support slow
storm motions. Little CIN on the 12Z soundings from WAL and IAD
suggest storm coverage will continue to increase with daytime
heating with the front and local terrain acting as sources for
lift. In addition, locally stronger easterly flow just behind the
cold front may help to support near-stationary convection along
the terrain of northern VA into northwestern MD and southern PA.

Given the lack of speed shear with height, storms should not be
organized in nature or long-lasting, but they should be rather
efficient with rainfall production given high wet bulb zero
heights of roughly 13 kft. Rainfall rates of 1-2 in/hr are very
likely with localized rainfall rates up to 3 in/hr possible. In
fact, rainfall rates from the HRRR support 1-2 inches of rain in
15 to 30 minutes which seems reasonable given the moist
environment. Portions of the Delmarva into southern MD and
southeastern PA received heavy rainfall yesterday and will be more
susceptible to localized flash flooding today. While flash
flooding is not expected to be widespread across the entire
region, scattered to numerous slow moving thunderstorms will
produce heavy rainfall with several areas at risk for flash
flooding, including the urban I-95 corridor from south of D.C.
into northern DE with 2-4 inches expected through 22Z.

Otto

ATTN...WFO...AKQ...CTP...LWX...PBZ...PHI...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 40587854 40517767 40357679 40047594 39547543
38187496 37767548 37877657 39167880 39907971
40507942
$$
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AWUS01 KWNH 101727
FFGMPD
MSZ000-LAZ000-ARZ000-102315-

Mesoscale Precipitation Discussion 0322
NWS Weather Prediction Center College Park MD
127 PM EDT Thu Jun 10 2021

Areas affected...central AR into northeastern LA and central MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 101722Z - 102315Z

SUMMARY...Backbuilding and training convection is expected to
continue areas of flash flooding for central MS and northeastern
LA, expanding northwestward into central AR through early evening.
Peak rainfall rates of 2-3 in/hr should continue and the overlap
with recent areas of heavy rain will exacerbate ongoing flooding.
An additional 3-5 inches is forecast through 23Z.

DISCUSSION...A long-lived complex of thunderstorms over the Lower
Mississippi Valley has shown a slow evolution over the past 6
hours toward the south and west. Low level cloud elements on
visible imagery continue to show a confluent pattern into the
tri-state region of AR/LA/MS where MRMS rainfall estimates ending
at 17Z have been near 4 in/hr in Issaquene County. A lack of
rainfall observations in the area has made it difficult to confirm
MRMS estimates, but the history of this complex and the efficient
environment make the MRMS rates seem reasonable. MLCAPE estimates
as of 17Z show 2000-3500 J/kg over northern LA into central AR
where mostly clear skies have allowed surface temperatures to
climb into the upper 80s while dewpoints are in the mid to upper
70s.

While winds at 850 mb have weakened since earlier this morning
into the 10-20 kt range, similar strength and direction of the
850-300 mb mean flow has supported backbuilding of storms into
southeastern AR. Short term forecasts from the RAP have been
consistent with maintaining the current strength and direction of
the low and mid-level flow into the early evening. Therefore, weak
to locally moderate low level confluent flow within the moist
environment and the presence of the right-entrance region of a
40-60 kt upper level jet streak to the north should continue to
support convective development over the next several hours.

Ongoing training near the LA/AR/MS junction may weaken in the next
2-3 hours in favor of increasing development into a expanding
cumulus field over central AR. The greatest confidence for an
additional 3-5 inches of rain exists across far western MS into
northeastern LA and southern AR, while convection to the north
(centarl AR) is expected to be more scattered in nature with
rainfall rates of 1-2 in/hr. Given heavy rain over the past 3
days, additional any added heavy rain will only worsen ongoing
flooding concerns.

Otto

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 35689213 35289148 34019055 33468979 33018917
32418911 32098970 32089100 32769240 33579289
34879299 35589275
$$
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AWUS01 KWNH 101802
FFGMPD
MDZ000-VAZ000-WVZ000-OHZ000-KYZ000-102300-

Mesoscale Precipitation Discussion 0323
NWS Weather Prediction Center College Park MD
201 PM EDT Thu Jun 10 2021

Areas affected...WV...southwest OH...Western & Southwestern VA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 101800Z - 102300Z

SUMMARY...Slow/Chaotic motions but ample deep warm cloud layer for
efficient rainfall through complex terrain.

DISCUSSION...GOES-E WV and Visible suite depict a vertically
sheared cyclone with 6.2um channel centered over western VA, 7.3
over central WV and IR/VIS channels showing compact center into
southwest OH. As a result, there is weak chaotic flow regimes,
though low level through 7H suggests southwesterly moist flow
across E WV into the front ranges of the Appalachians in western
VA and this is denoted well in the 850-7H Layer PW from CIRA.
Being on the western periphery of the upper-level waves has
supported some additional clearing for ample isolation and
building of instability. Mtn/Valley circulation combined with
some low level mass piling is supporting increasing agitation of
cu field both under the best mid-level cooling/upper-low but also
along the southeast quadrant of the lower circulation along/near
the Ohio River. Mid-level cloudy conditions have all but rendered
areas across far N WV into the western MD/Eastern WV panhandle
less conducive.

Deepest convective elements are forming with the better mid-level
lapse rates along the terrain of far E KY into W VA. Still, due
to deep warm cloud layer, ample moisture individual cells will be
highly efficient with up to 2"/hr rates. Cell motions will be
near zero further north and west with 5-10 kts toward the NNE
across southern portions of the MPD area. Hi-Res CAMs all suggest
best scattered 2-2.5" totals over E WV into W VA with the slightly
better 5-10 kts of inflow to help maintain updrafts more than the
"up and splat" nature further north and east,
propagating/regenerating along the outflows.

Still both modes have solid potential to exceed the low FFG in
complex terrain which is about 1"/hr though lower values of
.5-.75"/hr are nearer the low level cyclone convergence point.
Flash flooding is likely though it will be highly
scattered/locally focused to only a few watersheds...where some
neighboring watersheds may miss out totally.

Gallina

ATTN...WFO...JKL...LWX...MRX...PBZ...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 39598200 39578099 39458008 39277949 39047903
38157928 37377979 36738086 36788232 37348272
38158231 39158235
$$
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AWUS01 KWNH 201001
FFGMPD
FLZ000-GAZ000-ALZ000-201500-

Mesoscale Precipitation Discussion 0364...Corrected
NWS Weather Prediction Center College Park MD
601 AM EDT Sun Jun 20 2021

Corrected for Changed Areas Affected

Areas affected...Florida Panhandle, Southeast AL, Southwest GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 200951Z - 201500Z

Summary...Expanding coverage of thunderstorms in warm advection
ahead of an MCV will create an increasing flash flood risk this
morning. Multiple rounds of convection with rain rates to 2"/hr
are possible. Rainfall of 1-3" with isolated higher totals is
expected.

Discussion...A potent MCV stemming from a long-lasting forward
propagating MCS which has raced eastward overnight is now lifting
E/NE east of Hastings, NE. This MCV is being driven in part by a
robust and amplifying mid-level shortwave, and is moving into a
tropical airmass characterized by PWs around 1.5" and MUCape of
1500-2500 J/kg. A stationary front was analyzed draped west to
east along the MO/IA border, and recent VWPs indicate the 850mb
LLJ is increasing to 25-35 kts from the SW. This low-level SW flow
is isentropically ascending the stationary front, leading to
locally enhanced ascent across the region.

As the MCV continues to move eastward, ascent through PVA ahead of
the parent shortwave, isentropic upglide, low-level convergence
along the nose of the LLJ, and some enhanced acceleration east of
the MCV should maximize into the favorable thermodynamics. Recent
reflectivity from KEAX and KOAX indicate convection expanding
rapidly within the WAA regime and organizing due to bulk shear of
25-35 kts, with radar-estimated rainfall rates of 1-2"/hr becoming
common. While mean 850-300mb winds are robust to the E/NE at 20-30
kts, several rounds of heavy rainfall are possible during the next
few hours.

The HREF hourly rain probabilities suggest rainfall rates of 1-2"
will remain common through 12Z before beginning to wane as the MCS
moves into subtly drier air and the LLJ begins to veer, weakening
the ascent. During this time, rainfall of 1-3" is likely in many
locations as shown by the high-res guidance, and 6-hr HREF EAS
probabilities for 1" are above 60%, indicating both the agreement
of the members and the potential for excessive rainfall. While
recent rainfall has been modest during the past 14-days leading to
drier than normal soil moisture, there have been pockets of
rainfall 150% of normal during this time frame in SW IA. Here, FFG
is locally reduced to 1.5-2"/3hrs, and exceedance probabilities
are as high as 50%. Isolated flash flooding is possible through
early morning, but is most likely should this heavy rainfall occur
atop these locally more saturated soils.


Weiss

ATTN...WFO...BMX...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 32888426 32808366 32508303 32078261 31648242
31058232 30588228 30238243 29958259 29708287
29528332 29428379 29448447 29498495 29668553
29878601 30138625 30498637 31068626 31558597
32118552 32568511 32778480
$$
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AWUS01 KWNH 201923
FFGMPD
NCZ000-SCZ000-210122-

Mesoscale Precipitation Discussion 0366
NWS Weather Prediction Center College Park MD
323 PM EDT Sun Jun 20 2021

Areas affected...portions of North and South Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 201922Z - 210122Z

Summary...Gradually increasing convective coverage could result in
a few areas of flash flooding this afternoon and evening.

Discussion...Ahead of the eventual path of TD Claudette, strong
insolation amid a moist and increasingly buoyant airmass
(characterized by 2-2.3 inch PW values and around 2000 J/kg
MLCAPE) was fostering robust convective development recently. The
storms are in an environment with southwesterly flow aloft and
were moving northeastward at around 15-20 knots. However, the
weak low-level confluence and orientation of the development was
allowing for convection to repeat/develop in areas that have
received around 1-3 inches of rain earlier and have FFG values
ranging from 1-2 inch-per-hour thresholds. The very moist airmass
was allowing for rainfall rates to exceed these thresholds beneath
the heavier updrafts (up to around 2.5 inches per hour at times),
suggesting that at least a spotty flash flood threat should
materialize especially wherever training convection can occur.

Over time, convective coverage should continue to increase through
at least sunset due to continued insolation and low-level
convergence ahead of Claudette. There may be a downtick in
convective coverage thereafter due to loss of insolation, although
the moist environment should still sustain a few lingering storms
after sunset especially where updrafts can ingest non-convectively
modified air.

Cook

ATTN...WFO...AKQ...CAE...CHS...GSP...ILM...MHX...RAH...

ATTN...RFC...SERFC...NWC...

LAT...LON 36507687 35757645 35247670 34627730 33947811
33447893 32747988 32568062 32898137 33258164
34078207 34768161 35558024 36197842
$$
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AWUS01 KWNH 260932
FFGMPD
WIZ000-MNZ000-IAZ000-261500-

Mesoscale Precipitation Discussion 0387
NWS Weather Prediction Center College Park MD
531 AM EDT Sat Jun 26 2021

Areas affected...northeastern IA, southwestern WI and southeastern
MN

Concerning...Heavy rainfall...Flash flooding possible

Valid 260931Z - 261500Z

Summary...Slow moving showers and thunderstorms are expected to
produce locally heavy rainfall with rainfall rates of 2-3 in/hr
across portions of the Upper Mississippi Valley early this
morning. Localized rainfall totals of 3-5 inches will be possible
through 15Z.

Discussion...Regional radar imagery through 09Z showed
disorganized but slow moving showers and thunderstorms over
northeastern IA into southwestern WI. The activity was occurring
north of a stationary front that extended west-east across the
Mississippi River, out ahead of an 850-700 mb low centered over
eastern NE. While estimated instability was weak (500-1000 J/kg
via the SPC mesoanalysis), PWATs were high over the region (1.6 to
1.9 inches) supporting high rain rates. KARX rainfall estimates of
2-2.5 in/hr through 09Z over Allamakee County matched reports on
the ground, with radar-derived rates of 3+ in/hr over Crawford
County to the east. The region was located north of stronger
850-300 mb mean flow in place over MO and IL, with observed cell
motions of only 10-15 kt near the IA/MN/WI tri-state region. While
850 mb flow as also weak, repeating and training of storms has
been observed given the warm advection regime.

Warm advection and low level convergence is expected to continue
to support scattered showers/thunderstorms capable of producing
localized rainfall rates of 2-3 in/hr with slow movement of cells
contributing to isolated 3-5 inch rainfall totals through 15Z.
While much of the area has been dry over the past 1-2 weeks and
FFG is largely 3+ inches in 3 hours for much of the area,
efficient rainfall production may support some localized flash
flooding across portions of northeastern IA, southwestern WI and
southeastern MN this morning.

Otto

ATTN...WFO...ARX...DMX...MKX...

ATTN...RFC...NCRFC...NWC...

LAT...LON 44249048 43948956 43568938 43058946 42859089
42799199 42959245 43409260 44039186
$$
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AWUS01 KWNH 261229
FFGMPD
MOZ000-ARZ000-OKZ000-KSZ000-261700-

Mesoscale Precipitation Discussion 0388
NWS Weather Prediction Center College Park MD
828 AM EDT Sat Jun 26 2021

Areas affected...Southwest MO... Ext Northeast OK, Southaest KS &
Northwest AR...

Concerning...Heavy rainfall...Flash flooding possible

Valid 261230Z - 261700Z

SUMMARY...Ongoing early morning flash flood threat, slowly
diminishing...

DISCUSSION...Regional RADAR mosaic depicts NE to SW line of
thunderstorms across SW MO continuing to remain aligned parallel
to the deep layered steering flow within a broad large scale trof.
Typical of early morning convection at diurnal minimum in
instability, thunderstorms are taking on a more tendril appearance
with weak isentropic ascent across the remaining outflow boundary
with a stronger cell at the intersection of an MCV/weak shortwave
acting as a caboose to the train of thunderstorms with a solid
cold pool to aid in such acceleration.

While instability is waning overall, there is a remaining small
untapped pool along the leading edge across south-central MO at
the intersection of the preceding outflow boundary. As such
recent uptick was noted with overshooting tops/cooling tops on
GOES-E 10.3um. Nearly 100% saturated lowest levels and total
PWats over 2" and with solid 25-30kts of confluent
inflow/entrainment per SGF VWP support continued intense rainfalls
with rates over 2-2.5"/hr possible. Combine this with upstream
weaker but still efficient thunderstorms suggest training and
longer duration to support 2-4" of additional rain maintaining a
possible flash flooding threat over the next few hours.

Gallina

ATTN...WFO...SGF...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NWC...

LAT...LON 38149250 37759191 37039261 36419392 36229461
36399507 37109472 37789390
$$
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AWUS01 KWNH 262035
FFGMPD
MIZ000-INZ000-ILZ000-MOZ000-270300-

Mesoscale Precipitation Discussion 0391
NWS Weather Prediction Center College Park MD
434 PM EDT Sat Jun 26 2021

Areas affected...Central Illinois...Northwest Indiana

Concerning...Heavy rainfall...Flash flooding likely

Valid 262030Z - 270300Z

Summary...A slow moving, narrow line of thunderstorms will produce
a swath of 2-3 inches of rainfall atop already saturated soils
across central Illinois and northwest Indiana. Additional isolated
to scattered instances of flash flooding are likely.

Discussion...Thunderstorms along a narrow line are quickly
becoming more organized this afternoon, producing 2-3+"/hr
instantaneous rainfall rates (per the MRMS surface precipitation
rate product). This line is moving very slowly eastward, allowing
for training and realization of 1-hr rainfall totals of up to 1-2+
inches (based on KILX dual-pol estimates). The mesoscale
environment immediately downstream of this pre-frontal line of
thunderstorms is characterized by SB CAPE of 2000-3500 J/kg, PWATs
near 2.0 inches, and effective bulk shear of 20-30 kts. There is
not much forcing in this area of the warm sector, but these
atmospheric parameters will continue to sustain efficient rainfall
rates until daytime heating wanes later this evening. In addition,
the area is particularly vulnerable to rapid runoff due to already
saturated soils. NASA SPoRT 0-40 cm soil moisture percentiles are
above the 70-80th percentiles across much of the region, and 3-hr
flash flood guidance (FFG) reflects this with a significant
majority of the area below the 2 inch threshold.

Recent runs of the HRRR handle the current convection quite well,
and the eastward extension of a 2-3 inch swath of rainfall is
certainly believable. 12z HREF (3-hr) 2 and 3 inch neighborhood
exceedance probabilities are initially quite high (60% and 20%
respectively), but start to drop off into the evening. This should
limit the eastward extent of the 2-3" swath. That said, additional
training is likely in the meantime as the deep layer mean wind and
shear vectors initially parallel the orientation of the t'storm
line, eventually veering as the front begins to approach. Given
the aforementioned saturated nature of the soils, isolated to
scattered instances of flash flooding appear likely through this
evening.

Churchill

ATTN...WFO...ILX...IND...IWX...LOT...LSX...

ATTN...RFC...MBRFC...NCRFC...OHRFC...NWC...

LAT...LON 41818607 41638508 40478655 40008740 39408830
38708915 38168984 38329034 38879064 39389044
40388969 41108866 41788759
$$
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